Object Storage Service:Use a presigned URL to download an object (Python SDK V2)

The following sample code shows how to generate a presigned URL that allows HTTP GET requests for a specific version of an object:

import argparse
import alibabacloud_oss_v2 as oss

# Create a command-line parameter parser and describe the purpose of the script: generate a presigned URL for a GET request.
parser = argparse.ArgumentParser(description="presign get object sample")

# Add the --region command-line parameter to specify the region in which the bucket is located. This parameter is required.
parser.add_argument('--region', help='The region in which the bucket is located.', required=True)
# Add the --bucket command-line parameter to specify the name of the bucket that stores the object. This parameter is required.
parser.add_argument('--bucket', help='The name of the bucket.', required=True)
# Add the --endpoint command-line parameter to specify the domain name that other services can use to access OSS. This parameter is optional.
parser.add_argument('--endpoint', help='The domain names that other services can use to access OSS')
# Add the --key command-line parameter to specify the key of the object (file) in OSS. This parameter is required.
parser.add_argument('--key', help='The name of the object.', required=True)

def main():
    # Parse the command-line parameters to obtain the specified values.
    args = parser.parse_args()

    # Load the authentication information required to access OSS from environment variables for identity verification.
    credentials_provider = oss.credentials.EnvironmentVariableCredentialsProvider()

    # Use the default configurations of the SDK to create a configuration object and set the credential provider.
    cfg = oss.config.load_default()
    cfg.credentials_provider = credentials_provider
    
    # Set the region property of the configuration object based on the command-line parameters.
    cfg.region = args.region

    # If a custom endpoint is provided, update the endpoint property of the configuration object.
    if args.endpoint is not None:
        cfg.endpoint = args.endpoint

    # Use the preceding configurations to initialize the OSS client to interact with OSS.
    client = oss.Client(cfg)

    # Generate a presigned GET request.
    # Note: The version_id parameter is optional. You need to use this parameter only when versioning is enabled for your bucket.
    pre_result = client.presign(
        oss.GetObjectRequest(
            bucket=args.bucket,  # Specify the bucket name.
            key=args.key,        # Specify the object key.
            version_id='yourVersionId'  # Replace with the actual version ID if applicable.
        )
    )

    # Print the method, expiration time, and URL of the presigned request.
    print(f'method: {pre_result.method},'
          f' expiration: {pre_result.expiration.strftime("%Y-%m-%dT%H:%M:%S.000Z")},'
          f' url: {pre_result.url}'
    )

    # Print the signed headers of the presigned request.
    for key, value in pre_result.signed_headers.items():
        print(f'signed headers key: {key}, signed headers value: {value}')

# When this script is directly executed, call the main function to start the processing logic.
if __name__ == "__main__":
    main()  # The entry point of the script. The program flow starts here.

If you specify request headers when you generate a presigned URL for an HTTP GET request, you must include the same request headers in the GET request that uses the presigned URL. This prevents request failures and signature errors.

1. Generate a presigned URL that allows HTTP GET requests and contains specific request headers.

   import argparse
   import alibabacloud_oss_v2 as oss
   
   # Create a command-line parameter parser and describe the purpose of the script: generate a presigned URL for a GET request.
   parser = argparse.ArgumentParser(description="presign get object sample")
   
   # Add the --region command-line parameter to specify the region in which the bucket is located. This parameter is required.
   parser.add_argument('--region', help='The region in which the bucket is located.', required=True)
   # Add the --bucket command-line parameter to specify the name of the bucket that stores the object. This parameter is required.
   parser.add_argument('--bucket', help='The name of the bucket.', required=True)
   # Add the --endpoint command-line parameter to specify the domain name that other services can use to access OSS. This parameter is optional.
   parser.add_argument('--endpoint', help='The domain names that other services can use to access OSS')
   # Add the --key command-line parameter to specify the key of the object (file) in OSS. This parameter is required.
   parser.add_argument('--key', help='The name of the object.', required=True)
   
   def main():
       # Parse the command-line parameters to obtain the specified values.
       args = parser.parse_args()
   
       # Load the authentication information required to access OSS from environment variables for identity verification.
       credentials_provider = oss.credentials.EnvironmentVariableCredentialsProvider()
   
       # Use the default configurations of the SDK to create a configuration object and set the credential provider.
       cfg = oss.config.load_default()
       cfg.credentials_provider = credentials_provider
   
       # Set the region property of the configuration object based on the command-line parameters.
       cfg.region = args.region
   
       # If a custom endpoint is provided, update the endpoint property of the configuration object.
       if args.endpoint is not None:
           cfg.endpoint = args.endpoint
   
       # Use the preceding configurations to initialize the OSS client to interact with OSS.
       client = oss.Client(cfg)
   
       # Generate a presigned GET request.
       pre_result = client.presign(
           oss.GetObjectRequest(
               bucket=args.bucket,  # Specify the bucket name.
               key=args.key,        # Specify the object key.
               range_behavior="standard", # Specify a request header.
               request_payer="requester", # Specify a request header.
           )
       )
   
       # Print the method, expiration time, and URL of the presigned request.
       print(f'method: {pre_result.method},'
             f' expiration: {pre_result.expiration.strftime("%Y-%m-%dT%H:%M:%S.000Z")},'
             f' url: {pre_result.url}'
       )
   
       # Print the signed headers of the presigned request.
       for key, value in pre_result.signed_headers.items():
           print(f'signed headers key: {key}, signed headers value: {value}')
   
   # When this script is directly executed, call the main function to start the processing logic.
   if __name__ == "__main__":
       main()  # The entry point of the script. The program flow starts here.

2. Download the object using the presigned URL and specifying the request headers.

   curl

   curl -X GET "https://examplebucket.oss-cn-hangzhou.aliyuncs.com/exampleobject.txt?x-oss-date=20241113T093321Z&x-oss-expires=3599&x-oss-signature-version=OSS4-HMAC-SHA256&x-oss-credential=LTAI****************&x-oss-signature=ed5a******************************************************" \
   -H "x-oss-range-behavior: standard" \
   -H "x-oss-request-payer: requester" \
   -o "myfile.txt"

   Python

   import requests
   
   def download_file(signed_url, file_path, headers=None, metadata=None):
       """
       Downloads a file using a presigned URL.
   
       :param signed_url: The presigned URL.
       :param file_path: The full path to which the file is downloaded.
       :param headers: Optional. The custom HTTP headers.
       :param metadata: Optional. The custom metadata. This parameter is not used in GET requests.
       :return: None
       """
       if not headers:
           headers = {}
   
       try:
           response = requests.get(signed_url, headers=headers, stream=True)
           print(f"Returned download status code: {response.status_code}")
   
           if response.status_code == 200:
               with open(file_path, 'wb') as file:
                   for chunk in response.iter_content(chunk_size=8192):
                       if chunk:
                           file.write(chunk)
               print("File downloaded successfully")
           else:
               print("Download failed")
               print(response.text)
       except Exception as e:
           print(f"An error occurred: {e}")
   
   if __name__ == "__main__":
       # Replace <signedUrl> with the authorization URL.
       signed_url = "<signedUrl>"
       file_path = "/Users/yourLocalPath>/Downloads/downloadedFile.txt" # The local path to save the file.
   
       headers = {
           "X-Oss-Range-Behavior":"standard",
           "X-Oss-Request-Payer":"requester",
       }
   
       download_file(signed_url, file_path, headers=headers)

1. Generate a URL that contains the response-content-disposition parameter.

   import argparse
   import alibabacloud_oss_v2 as oss
   
   # Create a command-line parameter parser and describe the purpose of the script: generate a presigned URL for a GET request.
   parser = argparse.ArgumentParser(description="presign get object sample")
   
   # Add the --region command-line parameter to specify the region in which the bucket is located. This parameter is required.
   parser.add_argument('--region', help='The region in which the bucket is located.', required=True)
   # Add the --bucket command-line parameter to specify the name of the bucket that stores the object. This parameter is required.
   parser.add_argument('--bucket', help='The name of the bucket.', required=True)
   # Add the --endpoint command-line parameter to specify the domain name that other services can use to access OSS. This parameter is optional.
   parser.add_argument('--endpoint', help='The domain names that other services can use to access OSS')
   # Add the --key command-line parameter to specify the key of the object (file) in OSS. This parameter is required.
   parser.add_argument('--key', help='The name of the object.', required=True)
   
   def main():
       # Parse the command-line parameters to obtain the specified values.
       args = parser.parse_args()
   
       # Load the authentication information required to access OSS from environment variables for identity verification.
       credentials_provider = oss.credentials.EnvironmentVariableCredentialsProvider()
   
       # Use the default configurations of the SDK to create a configuration object and set the credential provider.
       cfg = oss.config.load_default()
       cfg.credentials_provider = credentials_provider
   
       # Set the region property of the configuration object based on the command-line parameters.
       cfg.region = args.region
   
       # If a custom endpoint is provided, update the endpoint property of the configuration object.
       if args.endpoint is not None:
           cfg.endpoint = args.endpoint
   
       # Use the preceding configurations to initialize the OSS client to interact with OSS.
       client = oss.Client(cfg)
   
       # Generate a presigned GET request.
       pre_result = client.presign(
           oss.GetObjectRequest(
               bucket=args.bucket,  # Specify the bucket name.
               key=args.key,        # Specify the object key.
               response_content_disposition="attachment;filename=test.txt",
           )
       )
   
       # Print the method, expiration time, and URL of the presigned request.
       print(f'method: {pre_result.method},'
             f' expiration: {pre_result.expiration.strftime("%Y-%m-%dT%H:%M:%S.000Z")},'
             f' url: {pre_result.url}'
       )
   
       # Print the signed headers of the presigned request.
       for key, value in pre_result.signed_headers.items():
           print(f'signed headers key: {key}, signed headers value: {value}')
   
   # When this script is directly executed, call the main function to start the processing logic.
   if __name__ == "__main__":
       main()  # The entry point of the script. The program flow starts here.

2. Use the presigned URL that contains the query parameters to download the specified object.

   curl

   curl -X GET "https://examplebucket.oss-cn-hangzhou.aliyuncs.com/exampleobject.txt?response-content-disposition=attachment%3B%20filename%3Dtest.txt&x-oss-date=20241113T093321Z&x-oss-expires=3599&x-oss-signature-version=OSS4-HMAC-SHA256&x-oss-credential=LTAI****************&x-oss-signature=ed5a******************************************************" \
   -o "myfile.txt"

   Python

   import requests
   
   def download_file(signed_url, file_path):
       """
       Downloads a file using a presigned URL.
   
       :param signed_url: The presigned URL.
       :param file_path: The full path to which the file is downloaded.
       :param headers: Optional. The custom HTTP headers.
       :param metadata: Optional. The custom metadata. This parameter is not used in GET requests.
       :return: None
       """
   
       try:
           response = requests.get(signed_url, stream=True)
           print(f"Returned download status code: {response.status_code}")
   
           if response.status_code == 200:
               with open(file_path, 'wb') as file:
                   for chunk in response.iter_content(chunk_size=8192):
                       if chunk:
                           file.write(chunk)
               print("File downloaded successfully")
           else:
               print("Download failed")
               print(response.text)
       except Exception as e:
           print(f"An error occurred: {e}")
   
   if __name__ == "__main__":
       # Replace <signedUrl> with the authorization URL.
       signed_url = "<signedUrl>"
       file_path = "/Users/yourLocalPath>/Downloads/downloadedFile.txt" # The local path to save the file.
   
       download_file(signed_url, file_path)

The following sample code shows how to use a custom domain name to generate a presigned URL that allows HTTP GET requests:

import argparse
import alibabacloud_oss_v2 as oss

# Create a command-line parameter parser and describe the purpose of the script: generate a presigned GET request.
parser = argparse.ArgumentParser(description="presign get object sample")

# Add the --region command-line parameter to specify the region in which the bucket is located. This parameter is required.
parser.add_argument('--region', help='The region in which the bucket is located.', required=True)
# Add the --bucket command-line parameter to specify the name of the bucket that stores the object. This parameter is required.
parser.add_argument('--bucket', help='The name of the bucket.', required=True)
# Add the --endpoint command-line parameter to specify the domain name that other services can use to access OSS. This parameter is optional.
parser.add_argument('--endpoint', help='The domain names that other services can use to access OSS')
# Add the --key command-line parameter to specify the key of the object (file) in OSS. This parameter is required.
parser.add_argument('--key', help='The name of the object.', required=True)

def main():
    # Parse the command-line parameters to obtain the specified values.
    args = parser.parse_args()

    # Load the authentication information required to access OSS from environment variables for identity verification.
    credentials_provider = oss.credentials.EnvironmentVariableCredentialsProvider()

    # Use the default configurations of the SDK to create a configuration object and set the credential provider.
    cfg = oss.config.load_default()
    cfg.credentials_provider = credentials_provider
    
    # Set the region property of the configuration object based on the command-line parameters.
    cfg.region = args.region

    # Set a custom domain name, such as "http://static.example.com".
    cfg.endpoint = "http://static.example.com"
    
    # Use a CNAME.
    cfg.use_cname = True

    # Use the preceding configurations to initialize the OSS client to interact with OSS.
    client = oss.Client(cfg)

    # Generate a presigned GET request.
    pre_result = client.presign(
        oss.GetObjectRequest(
            bucket=args.bucket,  # Specify the bucket name.
            key=args.key,        # Specify the object key.
        )
    )

    # Print the method, expiration time, and URL of the presigned request.
    print(f'method: {pre_result.method},'
          f' expiration: {pre_result.expiration.strftime("%Y-%m-%dT%H:%M:%S.000Z")},'
          f' url: {pre_result.url}'
    )

    # Print the signed headers of the presigned request.
    for key, value in pre_result.signed_headers.items():
        print(f'signed headers key: {key}, signed headers value: {value}')

# When this script is directly executed, call the main function to start the processing logic.
if __name__ == "__main__":
    main()  # The entry point of the script. The program flow starts here.